With particular reference to the known washing machines, the perforated basket, which is intended to accommodate the laundry to be washed, is rotatably arranged within a tank containing the lye. Due to the rotational movement of the basket, the laundry is agitated and caused to spin in the lye, and the lye is carried upwards by the rotating basket, from where it falls on the laundry which results to be completely immersed and soaked, such that the impurities are transferred to the washing and rinsing lye.
The basket usually consists of a rear wall by means of which the basket is secured within the washing machine, a front wall defining a loading opening through which it is possible to gain access to the interior of the basket and a side wall being generally cylindrical and perforated to allow the lye exchange between the tank and the interior of the basket. The side wall is usually formed from a steel sheet with two opposite longitudinal edges and two opposite transversal edges, which is folded about a longitudinal axis of the basket to form this cylinder and the transversal edges of which are connected to each other to keep the cylindrical shape, whereas the longitudinal edges are connected to respective outer edges of the rear and front walls to form the basket.
To increase the washing and drying performance on the laundry contained within the basket, the latter is exposed to increasingly greater loads of laundry, particularly because of an increase in the size and volume of the basket. In addition to the increase in the basket volume, attempts are made to operate baskets in washing machines with increasing rotational speeds and increasingly abrupt reversals of the direction of rotation. These operating conditions of modern washing machines and dryers imply, particularly during the spin cycle, high stress and dynamic deformations of the basket as well as the occurring of oscillations of the basket relative to the washing tank, which may result in the basket violently impacting against the wall of the washing tank housing the same. In order to certainly avoid the occurrence of these impacts, a minimum “safety” distance is required to be provided between the basket and the washing tank, any increase of the same inevitably resulting in an increase in the lye volume on the bottom of the tank, which cannot be used for washing purposes. The conflict is thus apparent between the requirement of increasing the washing performance and reducing the consumption of washing liquid and electric power required to heat this washing liquid.
To the purpose of avoiding said problems, solutions have been suggested which provide a truncated cone-shaped basket that is tapered towards the front wall or a cylindrical stepped basket that is tapered to the front wall (opposite the basket support point), such as to reduce the diameter size of the basket in that area where the oscillation width is the greatest. An example for this solution is disclosed in the European Application 044255503 by the same applicant.
It has been demonstrated, however, that these (large volume) baskets are not always suitable for use with traditional dragging blades extending in a substantially axial and rectilinear direction along the side wall of the basket. Due to the large diameter of the basket and the high number of revolutions, the tangent speed of the laundry at the blades is such that problems arise due to the laundry impacting against this type of dragging blades, which problems are not easy to control. An example is the phenomenon of instability or buckling of the side wall, which locally reverses the bending direction (known as “snap-through” of arc-shaped structures) and which is accompanied by a click-clack noise that is completely unacceptable in household appliances of this type. New solutions are thus sought for positioning and orienting the blades in order to avoid these problems. Naturally, due to the three-dimensionally curved shape of the basket side wall, a blade orientation other than the traditional one causes incompatibility problems between the shape of the blade root and the shape of the side wall and would oblige the manufacturers of washing machines and dryers to manage a range of various dragging blades according to various basket shapes and sizes.
In view of the general problems occurring in relation to large volume baskets, the general aim of the present invention is to provide a basket having such characteristics as to reconcile the requirements that have not been met or have been only partially met by the known solutions, and to the detriment of other requirements.
Within this general aim, the main object of the present invention is to provide a basket combining a high structural rigidity (against the deformations of the basket) with the possibility of allowing a different placement and orientation of the blades as compared with traditional ones without the requirement of arranging a range of various blades for various baskets.
A further object of the present invention is to avoid the problem of local instability (snap through) of the side wall at the dragging blades.
A further object of the present invention is to provide the basket with a shape that is fully consistent with what facilitates the achievement of said main objects and is further suitable to reduce the lye volume that is on the tank bottom, and which cannot be used for washing due to the safety distance between the basket and the tank.